Call function in R with arguments given in array form

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I have a function in R with a lot of default arguments, that I want to use multiple times. I want to be able to change those without having to write it all the time.

This is easy in Python like this:

def f(x, y, optional1=1, optional2=2, optional3=3):
    return (x+y+optional1+optional2+optional3)


args = (10, 20)
print(f(1,2, *args)) #this prints 36 = 1+2+10+20+3

now I have an R function f = function(x,y, optional1=1, optional2=2, optional3=3) but I have not found a way of doing something similar to the example above.

I was hoping something could be done with the ellipsis (...) but seems like that's only for a variable amount of arguments in the function definition.

Doing something like

g = function(x,y){
  return(f(x,y, 10, 20, 30)
}

would work but I was wondering if there was a cleaner and more readable way of doing this.

Thanks.

r function
1 Answers

There are a few ways, but you can use do.call().

f <- function(x, y, optional1 = 1, optional2 = 2, optional3 = 3){
  return(x + y + optional1 + optional2 + optional3)
}

f(1, 2, 10, 20)
# [1] 36

Using do.call() this will look like the following.

args <- list(optional1 = 10, optional2 = 20)
do.call(f, c(x = 1, y = 2, args))
# [1] 36

Another way using rlang saves a bit of typing, but is generally the same thing.

library(rlang)

exec(f, x = 1, y = 2, !!!args)
#[1] 36

If you are doing this a lot, you can take the approach you started and wrap a function.

g <- function(x, y, arg_list) {
  do.call(f, c(x = x, y = y, arg_list))
}

g(1, 2, args)
# [1] 36
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